Deploy HARP wrapper via model agent

README.md

@@ -1,5 +1,5 @@
 ---
-title: "MelodyFlow"
+title: "Melodyflow"
 colorFrom: indigo
 colorTo: gray
 sdk: gradio
@@ -9,7 +9,9 @@ pinned: false
 license: "other"
 ---
 
-# MelodyFlow
+# Melodyflow
+
+TODO: describe this model.
 
 - Inputs: textbox, slider, slider, checkbox, slider, slider, audio
 - Outputs: audio, audio, audio

app.py

@@ -1,6 +1,8 @@
 from __future__ import annotations
 
 import os
+import time
+import urllib.request
 
 import gradio as gr
 
@@ -12,6 +14,10 @@ _BACKEND_SPACE = "facebook/MelodyFlow"
 _BACKEND_API_NAME = "/predict"
 _BACKEND_TOKEN_ENV = "HF_TOKEN"
 _ACCEPT_USER_TOKEN = True
+# How many times to wake+retry a sleeping backend, and how long to wait for
+# it to boot (a free Space cold start can take a few minutes).
+_CALL_RETRIES = int(os.environ.get("BACKEND_CALL_RETRIES", "4"))
+_WAKE_TIMEOUT = float(os.environ.get("BACKEND_WAKE_TIMEOUT", "420"))
 _client = None
 
 
@@ -26,6 +32,54 @@ def _backend_client():
     return _client
 
 
+def _reset_client():
+    # Drop the cached connection so the next attempt reconnects to a Space
+    # that has since finished waking.
+    global _client
+    _client = None
+
+
+def _make_conn(tok):
+    tok = (tok or '').strip()
+    if tok:
+        return Client(_BACKEND_SPACE, hf_token=tok)
+    return _backend_client()
+
+
+def _space_url(space):
+    slug = space.strip().lower().replace('/', '-').replace('_', '-')
+    return f'https://{slug}.hf.space/'
+
+
+def _is_cold_start(message):
+    # Errors that mean 'the backend was asleep/booting', worth waking+retrying
+    # (vs. a real application error, which we surface immediately).
+    _low = (message or '').lower()
+    return any(s in _low for s in (
+        'read operation timed out', 'timed out', 'timeout', 'starting',
+        'building', 'not ready', 'no application', 'connection', '503', '502',
+    ))
+
+
+def _wake_backend():
+    # A sleeping Space boots when its URL is hit; poll until it answers (or
+    # the budget expires) so the retried call lands on a running backend.
+    _url = _space_url(_BACKEND_SPACE)
+    _deadline = time.time() + _WAKE_TIMEOUT
+    _delay = 5.0
+    while time.time() < _deadline:
+        try:
+            _req = urllib.request.Request(_url, headers={'User-Agent': 'harp-frontend'})
+            with urllib.request.urlopen(_req, timeout=30) as _resp:
+                if getattr(_resp, 'status', 200) < 500:
+                    return True
+        except Exception:
+            pass
+        time.sleep(_delay)
+        _delay = min(_delay * 1.5, 30.0)
+    return False
+
+
 def _quota_hint(message):
     # Turn a backend ZeroGPU quota error into an actionable message.
     # NOTE: 'message' is the backend's error text; it never contains our token.
@@ -55,25 +109,31 @@ model_card = ModelCard(
 
 def process_fn(text, steps, target_flowstep, regularize, regularization_strength, duration, melody, _hf_user_token=''):
     _tok = (_hf_user_token or '').strip()
-    if _tok:
-        _conn = Client(_BACKEND_SPACE, hf_token=_tok)
-    else:
-        _conn = _backend_client()
-    try:
-        _raw = _conn.predict(
-            'facebook/melodyflow-t24-30secs',
-            text,
-            'midpoint',
-            steps,
-            target_flowstep,
-            regularize,
-            regularization_strength,
-            duration,
-            handle_file(melody),
-            api_name="/predict",
-        )
-    except Exception as _exc:  # surface a token-aware hint, never the token
-        raise gr.Error(_quota_hint(str(_exc)))
+    # Call the backend, waking it and retrying if it was asleep (a cold
+    # start otherwise fails the first hit with 'read operation timed out').
+    _raw = None
+    for _attempt in range(_CALL_RETRIES + 1):
+        try:
+            _conn = _make_conn(_tok)
+            _raw = _conn.predict(
+                'facebook/melodyflow-t24-30secs',
+                text,
+                'midpoint',
+                steps,
+                target_flowstep,
+                regularize,
+                regularization_strength,
+                duration,
+                (handle_file(melody) if melody else None),
+                api_name="/predict",
+            )
+            break
+        except Exception as _exc:  # never surfaces the token
+            if _attempt < _CALL_RETRIES and _is_cold_start(str(_exc)):
+                _reset_client()
+                _wake_backend()
+                continue
+            raise gr.Error(_quota_hint(str(_exc)))
     _values = list(_raw) if isinstance(_raw, (list, tuple)) else [_raw]
     _detail = " | ".join(str(_v) for _v in _values if isinstance(_v, str) and _v.strip())
     _out_generated_audio_variation_1 = _values[0] if len(_values) > 0 else None